The invention relates to a rear axle suspension system for motor vehicles, in which the wheel carriers on both sides are coupled to the body of the vehicle in the transverse direction by means of at least one longitudinal link, one transverse link and a further guiding means. Such axle suspension systems are referred to as a longitudinal double transverse link axle or as a spherical double transverse link axle (Matschinsky: Die Radführung der Straβenfahrzeuge [Wheel guidance of road vehicles], Verlag TÜV Rheinland 1987, page 23). They may either be a driven or a non-driven axle.
The self-steering behavior of individual wheel suspension systems is usually configured so as to understeer for reasons of the dynamics of vehicle movement because this has a positive effect on driving safety when going round bends. However, it is disadvantageous that the steering movement of the wheel is less favorable in the driving behavior during spring compression when traveling straight ahead.
However, generally it is desirable to have a wheel suspension system which exhibits only a slight change in wheel position when traveling straight ahead but when cornering has a high degree of support of the lateral force, corresponding to a high rolling center. A perceptible change in the camber when cornering is also desired in order to compensate for the rolling movement of the vehicle body. Furthermore, if possible, there should be a tendency for the toe-in change in the direction of rolling understeering under the action of the side force.
Such a rear axle suspension system is known from DE 31 36 125 Cl, the further guiding means in the transverse direction being an upper transverse link. A coupling element is coupled to said transverse link and the lower transverse links are in turn coupled to it. As a result, when there is spring compression of both wheels in the same direction only slight changes in tracking and camber occur, but relatively large changes occur when there is spring compression in opposite directions. The length of the links remains however unchanged here so that the axle kinematics remain unchanged by this. In addition, it is not possible to achieve a side force steering effect in this way.
DE 36 34 090 A1 describes a rear axle steering system which is not of the generic type and in which an axle body which is rigid per se is guided at the wheel end on longitudinal links and in the center by means of a Watt linkage. The latter is intended to permit an elastic longitudinal, movement of the wheels without self-steering movement by virtue of a number of elastic connections. For this purpose, it is necessary to match the various elasticities, which is very difficult. Moreover, this axle structure acts kinematically like a conventional rigid axle which is guided by means of longitudinal links and a Watt linkage.
FR-A-1.191.743 discloses a wheel suspension system using a connecting transverse link and, on both sides, a further guiding means in the transverse direction, the transverse link being laterally supported by means of a straight-guiding means. As no longitudinal link is provided, the kinematics of a double transverse link axle whose lower transverse links are very long are obtained without any steering effects.
The object of the invention is thus to propose a rear axle suspension system of the generic type whose axle kinematics distinguish between spring compression in the same direction and spring compression in opposite directions and also permit the introduction of a side force steering effect, in particular in the direction of understeering.